Miller and Levine Biology Chapter 17

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Consists of all genes, including all the different alleles for each gene, that are present in a population.

Allele Frequency

The number of times an allele occurs in a gene pool, compared to the total number of alleles in that pool for the same gene.

Single-gene Trait

A trait controlled by only one gene.

Polygenic Traits

Many traits are controlled by two or more genes; each gene usually has two or more alleles.

Directional Selection

When individuals at one end of the curve have higher fitness than individuals in the middle or at the other end.

Stabilizing Selection

When individuals near the center of the curve have higher fitness than individuals at either end.

Disruptive Selection

When individuals at the outer ends of the curve have higher fitness than individuals near the middle of the curve.

Genetic Drift

Random change in allele frequency caused by a series of chance occurrences that cause an allele to become more or less common in a population.

Bottleneck Effect

A change in allele frequency following a dramatic reduction in size of a population.

Founder Effect

Allele frequencies change as a result of the migration of a small subgroup of a population.

Genetic Equilibrium

If a population is not evolving, allele frequencies in its gene pool do not change.

Hardy-Weinberg Principle

Allele frequencies in a population should remain constant unless one or more factors cause those frequencies to change.5 conditions required: very large population, no mutations, random mating, no movement into or out of population, no natural selection

Sexual Selection

Individuals select mates based on heritable traits, such as size, strength, or coloration.

Species

A population or group of populations whose members can interbreed and produce fertile offspring.

Speciation

The formation of a new species.

Reproductive Isolation

When two populations no longer interbreed.

Behavioral Isolation

Form of reproductive isolation in which two populations develop differences in courtship rituals or other behaviors that prevent them from breeding.

Geographic Isolation

When two populations are separated by geographic barriers such as rivers, mountains, or bodies of water.

Temporal Isolation

When two or more species reproduce at different times.

Molecular Clock

Uses mutation rates in DNA to estimate the time that two species have been evolving independently.

Extinct

A species which has died out.

Population

group of individuals of the same species that mate and produce offspring

Relative frequency

the number of times a particular allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur

Evolution

any change in the relative frequency of alleles in the gene pool of a population over timePopulations evolve; people do not

Lateral gene transfer

genes passed from one individual to another that is not its offspring - increases genetic variation Ex: viruses transfer genes between organisms